The present invention relates generally to the automotive chain drive art and, more particularly, to a mechanical blade-type chain tensioner apparatus useful in confined spaces for applying a tensioning force to a chain traveling there past. Such blade-type chain tensioning devices include a chain engaging blade or shoe member, typically molded from a polymeric resinous or “plastic” material, having a metal spring installed therein to provide the shoe sub-assembly with the necessary rigidity and damping characteristics while taking advantage of the flexibility, low friction, and good wear properties of the plastic shoe.
FIG. 1 shows a known blade-type tensioner apparatus T′ comprising a bracket K′ typically defined from a metal stamping and a tensioner blade assembly BAS′ operably secured to the bracket. As shown in FIG. 1B, in use, the bracket K′ is fixedly secured to an associated engine block EB as part of a chain drive system that is provided to phase or “time” the rotational position of one or more camshaft sprockets CMS with respect to the rotational position of the crankshaft sprocket CKS. One or more bolts or other fasteners BT′ extend through mounting apertures KA′ in a main wall MW′ of the bracket K′ and are threaded into the engine block EB or other associated support structure to fixedly secure the bracket K′ in its operative position. A chain 15 such as a roller/bush chain or inverted tooth chain is engaged with the crankshaft sprocket CKS and the camshaft sprocket(s) CMS and phases/times the camshaft sprocket(s) to the crankshaft sprocket. The crankshaft sprocket CKS rotates in a direction DIR, and the chain 15 includes a taut strand portion 16 and a slack strand portion 17.
The illustrated known tensioner T′ comprises an optional first portion T1′ that comprises a fixed guide flange XF′ that projects transversely from the main wall MW′ of the bracket K′ and that is engaged with and supports a fixed chain guide FG′ defined from a polymeric resinous material. The fixed chain guide FG′ includes a guide face that slidably engages and supports/guides the taut strand 16 of the chain as shown in FIG. 1B.
The tensioner T′ further comprises a second portion T2′ comprising the blade assembly BAS′. As part of the tensioner second portion T2′, the bracket K′ comprises a cold-headed steel or other pin N′ that projects perpendicularly outward from the main wall MW′ and that is welded or otherwise securely affixed to the main wall MW′. FIG. 1A is a section view taken at line 1A-1A of FIG. 1 (of the bracket K′ only without showing the blade assembly BAS′) that shows the pivot pin N′ secured to the main wall MW′ of the bracket by a resistance weld or other weld NW′. As part of the tensioner second portion T2′, the bracket K′ further comprises a support flange TF′ that projects outwardly from the main wall MW′. An end of the support flange TF′ forms or defines a ramp R′, and an outer wall OW′ extends transversely from an outer end of the ramp R′ and extends parallel to the main wall MW′ such that a channel CH′ (FIG. 1A) is defined between the main wall MW′, the outer wall OW′, and the ramp R′.
A known tensioner blade assembly BAS′ is operatively connected to the bracket K′ and includes a polymeric or “plastic” shoe S′ and a metal spring G′ releasably connected to the shoe S′. A first or pivot end S1′ of the blade assembly BAS′ includes a boss or barrel S4′ that includes pivot bore SB′ that is slidably received onto the pivot pin N′. An opposite second or free end S2′ of the blade assembly BAS′ is located in the channel CH′ and supported on the ramp R′. A retaining pin RP′ shown in FIG. 1 is used for shipping and handling only to secure the free end S2′ on the ramp R′ and is removed for operation of the blade assembly BAS′ as shown in FIGS. 1B and 1C. The bracket K′ maintains the blade assembly BAS′ in its proper position with respect to the plane of the chain path while permitting sliding reciprocal translational motion of the second, free end S2′ on the ramp R′ as indicated by the arrow “TRANS” along with the related reciprocal angular or rotational movement of the blade assembly BAS′ at the pivot end S1′ as indicated by the arrow labeled “ROTATE” in response to changes in the tension and position of the slack strand 17 of the chain 15 and corresponding oscillatory movement of the slack strand 17 as indicated by the arrow “AMPL.” FIG. 1C is a partial view of the tensioner T′ that shows this operative movement of the blade assembly BAS′ using solid lines for a first (bowed) position of the blade assembly BAS′ and phantom lines for a second (compressed) position of the blade assembly BAS′.
The pivot pin N′ can be replaced by a shoulder bolt or any other suitable fastener that extends through the shoe pivot bore SB′ and through the bracket main wall MW′ and that is threaded into the engine block EB or other associated support structure to allow rotation of the pivot end S1′ of the shoe S′ relative to the bracket K′. In either case, whether the tensioner T′ comprises a pivot pin N′ or a shoulder bolt, in certain engine environments, the packaging environment is limited such that a stamped steel bracket with sufficient structural integrity cannot be packaged in the available space, or a stamped steel bracket K′ is sometimes disfavored due to the required fixing/mounting point positions or for other packaging or design related reasons. As such, it has been deemed desirable to provide an alternative tensioner and tensioner bracket structure.